O ct 2 00 4 Magnetic properties and thermal expansion of YbGa x Ge 2 − x ( 0 . 9 ≤ x ≤ 1 . 5 )

The composition dependence of the Yb valence and of the thermal expansion have been studied in the YbGaxGe2−x system. X-ray diffraction reveals that singlephased samples isostructural to YbGaGe are obtained in the range of 0.9 ≤ x ≤ 1.5. The magnetic susceptibility shows that the systems are almost nonmagnetic below room temperature, indicating a stable Yb state for the x range 0.9 ≤ x ≤ 1.5. The lattice constants as well as the lattice volume of these systems are found to decrease monotonically with decreasing temperature, suggesting the absence of zero thermal-expansion previously reported for YbGaGe.